There has been known a navigation system which can be utilized as a guide by detecting the present position accompanying the traveling of a vehicle relying upon the GPS or the like, displaying the present position on a display unit together with a road map, and setting a suitable route from the present position to a destination, contributing to a smooth driving. The route is usually set by utilizing the Dijkstra method or the like method. Concretely speaking, route calculation costs (evaluated values for the route) from the present position to the nodes are calculated by using the map data stored in a static source of data such as a CD-ROM or DVD-ROM and by using the link data for the links among the nodes. Links that make the total cost a minimum are connected at a step where the calculation of the total cost up to the destination has finished to set the route to the destination.
Further, when the route is calculated based on only the data of the static source of data, it is not allowed to add dynamic varying traffic conditions to the conditions of calculation. Therefore, the route to the destination may include a road having congested traffic due to, for example, construction or a traffic accident that has not been recorded as static data. Therefore, there have been conceived systems for receiving traffic regulation data from a dynamic source of data or for receiving a recommended route by adding traffic regulation data thereto, such as ATIS or VICS employed in Japan and RDS-TMC employed in European countries. In a navigation device receiving the data specifying a portion where the traffic is congested, for example, the route cost of the congested portion is increased to be greater than what it usually is. This permits limited inclusion of the congested portion in the route, thereby making it possible to automatically set a detour avoiding the congested portion caused by the construction or traffic accident as mentioned above. The same also holds even when the detour itself is received from the dynamic source of data.
However, even if the traffic is not congested, the user may often wish to avoid a particular traveling area due to individual circumstances. According to the above method based on the static source of data or the dynamic source of data, the particular traveling area cannot be avoided to meet the user's knowledge or individual circumstances. Therefore, a technology has been disclosed enabling the user to set an avoided area based on the user's determination and to set a route to avoid the above area (see, for example, a patent document 1).
The avoided area may be a regulated area in the road pricing system for relaxing the congested portion or for improving the air pollution (hereinafter referred to as road pricing area) (see non-patent document 1). Entry into the road pricing area requires permission (entrance permission: area license), and such permission must be obtained in advance, such as, for example, a determining period of one day, one week, one month or one year. There will be no problem to travel through the load pricing area if the area license is valid. If the area license is not valid, however, a fine will be imposed if the user travels through the load pricing area.
Therefore, even the road pricing area may be set as the avoided area when the area license is not valid to automatically set a detour avoiding the road pricing area.
[Patent document 1] JP-A-11-83519
[Non-patent document 1] Description related to the road pricing in the home page of Tokyo Metropolitan Environment Bureau [online], updated: Nov. 13, 2004 [retrieved on Mar. 11, 2004],
When the road pricing area is to be set as an avoided area according to the conventional method, however, the user must determine whether the area license is valid/invalid at the time of setting the route based on the valid term of the area license, and must set the road pricing area as the avoided area when the area license is invalid. Therefore, the road pricing area must be set to be the avoided area every time the area license is obtained or every time the area license becomes invalid (every time the valid term expires), and must reset it, requiring very cumbersome operations. If the user forgets to do the above actions, the user may travel through the road pricing area despite the area license being invalid and be possibly fined.
The above problem is not limited to the above road pricing areas but may similarly occur in regulated areas where entrance is limited based on permission.